A bit difficult to trace the exact sequence so long after I have looked at it - but baring any mistakes this seems to be it
1 Switch 213LTAP in 60SAD to both day and night missions
2 Switch to transport mode, select airbase, shift and right click
The transport mission is a success!
2 Switch to rail repair map info
selecting the base it will now look like this
3 It will now no longer work when you go through the same process of setting up an air supply